SOUTH SAN FRANCISCO — Things moved at a rapid pace during Friday night’s matchup between San Mateo and host South San Francisco.

On the visiting side, you had nimble and fleet-footed Vai Liu. On the other, you had Sam Seuma’ala, who tallied a game-high 80 yards on 16 carries.

But it was the speed of the defense that gave South City a 40-20 victory Friday in the Peninsula Athletic League Bay Division. The Warrior pass rush caused a pair of San Mateo quarterbacks to throw three interceptions. Their defense forced three fumbles and collected three sacks.

“That group of linebackers can run,” said SSF coach Frank Moro. “They can outrun any offense, I think.”

It was a simple strategy, according to South City linebacker Bert Frisby.

“We really wanted to shut down Vai Liu,” he said.

The Warriors (6-1, 4-1 PAL Bay) got off to a great start when John Mark Henderson took the opening kickoff back 76 yards to the San Mateo 16, setting up Saul Mora’s 4-yard touchdown run. South San Francisco upped its lead to 14-0 on its next possession, asquarterback Eric Moore ran in a six-yard keeper.

San Mateo (3-4, 1-3) got within a touchdown with just over one minute left in the first quarter when Brian Maile hooked up with Kalepi Kautai on 13-yard TD pass.

South City responded with another keeper by Moore, for eight yards with 4:38 before the half, and appeared poised for more when the Bearcats got a bit of luck.

Seuma’ala looked as if he was going to put his squad up by three touchdowns when a hard tackle jarred the ball loose on the San Mateo 6. Liu (69 yards rushing, TD) picked up the fumble and almost appeared to go down twice, then ran 94 yards up the right sideline for a Bearcats’ touchdown — his second fumble recovery for a touchdown in four games.

While San Mateo quarterbacks Maile and Danny Weber kept the offense moving, too often their drives were halted by turnovers. The Bearcats lost three in each half, while South City never gave up the ball.

“I can’t fault my quarterbacks for playing their butts off,” San Mateo coach Mike Parodi said. “They’re both juniors, they’re both learning and we deal with that. I think for the most part our team played pretty well, but (South San Francisco) is pretty darn good.”

South City finds itself in good position for the Central Coast Section playoffs with only one loss and two divisional games — including a tussle with Woodside next week — remaining.

“I think we’re working toward the playoffs,” Frisby said. “I think this team really wants it bad, so I think we’re going to go.”